Process of detinning tin-scraps, &amp;c.



r and clean non-corroding surface.

reason why the alkalme processes are prefer- .i so

UNITED STATES PATENT OFFICE.

KARL GOLDSCHMIDT AND JOSEF WEBER, OF ESSEN-ON-THE-RUHR, GERMANY, ASSIGNORS TO THE FIRM OF TH. GOLDSCHMIDT, OF ESSEN-ON-THE-RUHR, GERMANY.

PROCESS OF DETINNING TlN-SCRAPS, 620-. v

Specification of Letters Patent.

Patented Nov. 20, 1906.

Application filed Tuna 29,1905. Serial No. 267,581.

Empire, have jointly invented certain new and useful Improvements in the Processes of the Recovery of Detinned'Sheet-Iron from Tin-Scraps or Tin-Plates, of which the following is an exact specification.

.The known processes for the recovery of tin from tin-plate waste by means of acids,

acid salts, or chlorin do not leave the sheetiron with a permanently-clean surface.

Whether the separation of the tin is effected I by known processes purely chemically or electrolytically, the surface of the sheet E metal treated is corroded or will easily corrode and though subjected to a washing process is extremely liable to rust subsequently, so that the sheet-iron isof little use, or at least greatly reduced in value for treatment On the other hand, it is known that in alkaline processes the sheet-iron receives the desired bright in Siemens-Martin hearth-furnaces.

This is the ably used at present for the urpose, though much more cumbersome an expensive than those based on acids.

It has now been discovered by us that it is possible to obtain the sheet-iron with a bright 1 steel-gray surface by chemical treatment if the tin-plate is treated with chlorin gas in a dry process to be further described and that the clean and bright surface of the detinned' tin-scraps may be maintained and the detinned tin-scraps protected against rusting by the following process: When the detinning of the tin-scraps being finished, it is necessary surfaces of the tin-scraps or which are in the vessel in which the detinning process had taken place. This is effected by diminishing the pressure in the rece tacle or vessel in which-the detinning process ad been finished.

The vessel is evacuated by an air-pump, and so the residue of the chlorid-of-tin gases and of the chlorin gases is removed by this ventilating or exhausting process. The detinned tin-scraps are perfectly free from those materials. They are subjected to a washing process with water, whereby the chlorid of iron which is formed on the surfaces of the detinned tin-scraps by the above-described detinning process is removed.

We will now completely describe our process.

The tin-scraps are first submitted in a suit able receptacle of brickwork, stone, iron, and the like to the action of dry chlorin vapors, preferably in a closed apparatus. Care is taken that the chlorin acts on the tin-plate in a weak or diluted condition, and we use the tin-scraps preferably in mechanically-compressed condition, because this has the advantage when carrying out the process on a large scale that vessels of comparatively small dimensions can receive a large quantity of waste, and it has been found that the close packing of the numerous pieces of tin-plate waste does not prevent the complete recovcry of the tin and the production of bright non-corroding sheet-iron waste in the whole process hereinafter described.

The chlorin process is carried out as a dry process and is conducted in such a manner that as far as possible anhydrous chlorid of tin is produced free from iron, and the tem perature of the tinlate waste is kept as low as possible. After t is tin-separation process the last remnants of chlorid of tin are removed from the apparatus through clearing the latter by placing it under a vacuum. This sheet-iron waste freed from the tin is nowfree from the adhering remains of the chlorid-of-tin vapors by the ventilating or exhausting process,- but a firmly-adhering thin layer of chlorid of iron has been formed on the sheet-iron waste, though the process has been carried out in a dry manner. This thin layer of chlorid of iron results, in our opinion, from an intermediate layer existing between the actual sheet-iron and the layer of tin on the tin-plates and which may be a kind of alloy of iron and tin. Therefore while the outer layer of pure tin is entirely dissolved with a bright steel-gray surface.

by the chlorination process and while the iron is not-attacked by this dry process in which weak chlorin gas is used the layer of alloy is affected, which explains, in our opinion, the presence of chlorid ofiron on the waste from which the tin has been separated. This remaining layer or the Y articles of chlorid of iron are the cause of t e subsequent corrosion of the treated sheet-iron waste which has been obtained by the separation process This chlorid of iron can now be removed by'a washing process with water without danger that a corrosionoftheimn sheet takes place, the remnants of the reacting agents being perfectly removed from the detinned scraps. By

this washing process the-chlorid of ironis.

dissolved and by a subsequent flushing with alkaline lye the iron sheets are perfectly protected. This washing process with water and eventually-a subsequent process of treat ment with'al'kaline lye are known 61 se in a certain wet chemical process-fort etre'atment of tin-plate waste 'with'a solution of chlorid of iron, (see United States Patent No. 480,920,) but the difference between thisprocessan'd ours is great and important, because inthe wet treatment of sheet'metal waste-referred to direct'with chlorid of iron obviously the sheet-iron itself is attacked as well as the before-mentioned intermediate layer and causes corrosion. This takes place as-the solution of-chlorid of iron naturally attacks the iron ver strongly; but the dry chlorid of iron'whic is formed in our dry chlorin process does not attack pure iron and therefore does not attack the-sheet-iron.

It may be obvious to combine a wet sparation process with a wet washing process but it is'not at all obvious to combine a dry separation process in which the presenceof any water has been carefully avoided with a washing process to succeed the dry separationprocess after all remnants of the acting agents are previously removed by an exhausting process or by an evacuating process.

To describe once more the process, we act as follows: After the separation of the tin has been completed and the last remains of the chlorid of tin have 'been evaporated and removed by the evacuation of the receptacle andwhen the last remains of chlorin which have not yet come into action are thus'removed from the receptacle the bundles of iron are washed in water. This washing process is advantageously shortened by placing the'bundles of iron first into a separate closed apparatus which is evacuated and into which Water is then admitted. All intermediate spaces are now energetically flushed with water. This process may be repeated and the process may be carried out underalternating'pressure. After the bundles have been in this manner sufficiently flushed with water they are dipped into a weak alkaline bath, and in-this manner a thin protective layer of the saltused therein is formed. The sheet-iron thus receives a permanently bright steel-gray surface without any essential signs of corrosion.

Having thus fully described the nature of our invention, What We desire to secure by Letters Patent of the United States is- 1. Process of the recovery of detinned sheet-iron from tin-scrap or tin-plate, consisting in subjecting the tin-scrap or tinplate to the action of chlorin in a receptacle and removing the reagent and the chlorid of tin in a dry state and afterward washin the sheet-ironin water for'removing the c orid of iron adhering to the tin-scrap or tin-plate.

2. The process of the recovery of detinned sheet-iron from ti'n sc'rap or ti'nplate,'consisting in subjecting the tin-scrap or tinplate to the action of chlorinin a receptacle, and removing the reagent and the chlorid of tin, and afterward washing the sheet-iron in water for removing the chlorid of iron'ad hering to the tin scrap or tin-plate. v

3. Process of the recovery of detinned sheet-iron from tin-scrap or tin-plate, con sisting in subjecting the tin-scrap or tinplate in compressed state to the action of chlorin in a-recepta'cle and removing the reagent and the gaseous products of-the reaction by evacuating the receptacle and afterward washin the sheet-iron inwater for removingthec oridof iron.

4. Process of the recovery of detinned sheet-iron from tin-scrap or tin-plate, consisting in subjecting the tin-scrap or tinplate tothe action of chlorin in a receptacle and 'removing'thereagent-and the gaseous products of the reaction and afterwardwashin the sheet-iron in water for removing the ch orid of iron and then-subjecting it to the action of an alkaline solution.

5. Process of the recovery of detinned sheet-iron from tin-scrap or tin-plate, consisting in subjecti'n plate to the action 0% chlorinin a receptacle and removing'the reagent and the 'gaseous products of the reaction in a dry state and afterward washing the sheet-iron in water for removing the chlorid of iron and then subjecting it to the action of an alkaline solution.

'6. Process of the recovery of detinned sheet-iron from tin-scrap or tin=plate, consisting in subjectin the tin-scrap or tinplate to the action 0% chlorinin a receptacle and removing the reagent and the gaseous products of the reactionand afterward Washing the sheet-iron by circulating Water under pressure between the'sheets for removing the chlorid of iron.

7. Process of the recovery of detinned sheet-ironfrom tin-scrap or'tin pla te, consisting in-s'ubjecting the tin scrap or tfn 'plate to the action of chlorin in a receptacle and rethe tin-scrap or tinmoving the reagent and the gaseous products of the reaction and afterward washing the sheet-iron by circulating water under pressure between the sheets for removing the chlorid of iron and then subjecting it to the action of an alkaline solution.

8. Process of the recovery of detinned sheet-iron from tin-scrap or tin-plate, consisting in subjecting the tin-scrap or tin-plate to the action of chlorin gases in a receptacle and removing the reagent and the gaseous products of the reaction and afterward washing the sheet-iron in water for removing the chlorid of iron.

9. Process of the recovery of detinned sheet-iron from tin-scrap or tin-plate,'consisting in subjecting the tin-scrap or tin-plate to the action of chlorin gases in a receptacle and removing the reagent and the gaseous products of the reaction in a dry state and afterward washing the sheet-iron in water for removing the chlorid of iron.

10. Process of the recovery of detinned sheet-iron from tin-scrap or tin-plate, consisting in subjecting the tin-scrap or tin-plate in compressed state to the action of chlorin gases in a receptacle and removing the reagent and the gaseous products of the reaction by exhausting the receptacle and afterward Washing the sheet-iron in water for removing the chlorid of iron.

11. Process of the recovery of detinned sheet-iron from tin-scrap or tin-plate, consisting in subjecting the tin-scrap or tin-plate to the action of chlorin gases in a receptacle and removing the reagent and the gaseous products of the reaction and afterward washing the sheet-iron in'wate'r for removing the jecting it to the action of an alkaline solution.

13. Process of the recovery of detinned sheet-iron from tin-scrap or tin-plate, consisting in subjecting the tin-scrap or tin-plate to the action of chlorin gases in a receptacle and removing the reagent and the gaseous products of the reaction and afterward washing the sheet-iron by circulating water under pressure between the sheets for removing'the chlorid of iron.

14. Process of the recovery of detinned sheet-iron from tin-scrap or tin-plate, con sisting in subjecting the tin-scrap or tin-plate to the action of chlorin gases in a receptacle and removing the reagent and the gaseous products of the reaction and afterward washing the sheet-iron by circulating water under pressure between the sheets for removing the chlorid of iron and then subjecting it to the action of an alkaline solution.

In witness whereof we have hereunto set our hands in the presence of two witnesses.

KARL GOLDSOHMIDT. J OSEF WEBER. 

